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Modbus Master Point Attributes
Figure 19: Edit Modbus Master Attributes
• Edit Address: Menu selection 1 allows you to edit the network
address of the Modbus slave that this point refers to.
• Edit Register: Menu selection 2 allows you to edit the Modbus
holding register or input register that this point will access. The type of
register accessed (holding or input) will be determined on the basis of
the “Read FC” setting (see below). Figure 19 shows an example of
how to change the current setting of register 1 to register 50.
• Read FC: Menu selection 3 allows you to choose the Modbus “read”
function code that will be used to read from the designated register.
The default setting of function code 03 (read holding registers) will
access a holding
register on the remote device. By selecting function
code 04 (read input registers), a Modbus input
register will be
accessed instead.
• Write FC: Menu selection 4 allows you to choose the Modbus “write”
function code that will be used to write to the designated holding
register (this setting does not apply to input registers, as they are
read-only). The default setting is function code 16 (preset multiple
registers). Alternatively, this setting can be changed to function code
06 (preset single register) in order to connect to those Modbus slave
devices that do not support function code 16.